The need for ever-smaller pumping devices, particularly in the medical field, continues to grow. As a result, the need for increasingly small operational pump components is growing as well, challenging the limits of conventional manufacturing processes. As fluidic devices shrink, it is necessary to manufacture fluidic paths with very tight radii and varying cross-sections to fit within the device package. Some of these cross-sections may not be round, and it may be necessary to form fluidic connectors directly into the fluid paths themselves.
Conventional manufacturing techniques have various limitations. One approach to creating polymeric fluidic paths is to use photoresist to create a channel in a layered polymer. Once the polymer has been layered over the photoresist, it is dissolved to leave a fluid channel; see, e.g., Jason Shih, 2008 “Microfabricated High-Performance Liquid Chromatography (HPLC) System With Closed-Loop Flow Control,” Ph.D. thesis, Department of Mechanical Engineering, California Institute of Technology. Another approach is to use polymer extrusion to create small fluid channels; see, e.g., Lopez, Fernando L., 2011, “Micro-Sized Components for Medical Extrusion,” Interface Catheter Solutions, California, USA. This is a standard method of fabrication for catheters and other macro-scale tubes. Although varying interior diameters and wall thicknesses are achieved by manipulating extrusion speed and die configurations, shapes such as tight-radius twists and bends are not easily replicable. A third approach is three-dimensional (3D) wax printing to create other types of structures for use in devices. This approach has been used to create relatively large 3D structures coated with very thin polymer layers; see, e.g., Feng, Guo-Hua and Kim, Eun Suk, 2003, “Universal Concept for Fabricating Micron to Millimeter Sized 3D Parylene Structures on Rigid and Flexible Substrates,” The Sixteenth Annual International Conference on Micro Electro Mechanical Systems, 2003, pp. 594-597.
Unfortunately, conventional approaches such as these do not readily allow for the creation of fluid paths of a tortuous nature, having varying radii and minute dimensions, and with a smooth finish as necessary for long-term use, especially in implantable drug pumps. Smooth fluid paths within an implantable drug pump are generally necessary to avoid or minimize structures that promote drug aggregation, to reduce clogging, and to avoid long-term biofouling. A particular challenge in conventional manufacturing techniques is integrating flow-altering structures such as filters into a fluid path.